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Bok Prize for research that breathes new life into astronomical images

12 July 2013

PhD student Ben Pope received the highest award given by the Astronomical Society of Australia for research conducted by an honours student.

Research using a new technique to analyse archival images from the Hubble Space Telescope has won a University of Sydney PhD student the prestigious 2013 Bok Prize.

Ben Pope yesterday received the highest award given by the Astronomical Society of Australia for research conducted by an honours student.

Pope's citation from the Astronomical Society singled out the important potential for new discovery of his research by delivering the first scientific results with a new image analysis technique. The research promises to breathe new life into high resolution astronomical imaging.

"The Hubble Space Telescope has been a truly remarkable observatory, but despite the extreme competition to use it, a lot of the images taken with it have never been analysed to their full potential," explained Pope.

"The data I used for my research was mostly taken around 2005… and it had been sitting on a public archive since then. This data had previously been studied by simple visual inspection, but contained a hidden trove of discoveries accessible only after advanced computer processing."

"The thing that made all the difference for us was being able to apply the very latest leading-edge image analysis technique called kernel phase interferometry. I was fortunate enough to learn about this straight from its inventor, Dr Frantz Martinache, on a visit to Hawaii last year. Together we made the first new discoveries with this powerful new approach," said Pope.

It turns out that despite all the effort and expense, even the multi-billion dollar Hubble Space Telescope does not yield absolutely perfect vision.

The mirrors, lenses and other components that comprise the telescope all bend and warp by tiny amounts as the observatory orbits in space, enough to create subtle shifts in the image that are easy to confuse with real signals from the star being studied. The key breakthrough came with the realisation that the structure in the image could be mathematically divided into two classes: firstly those which could arise from errors in the mirror, and critically, a second class which could not.

"In essence, we divide the image into two parts," explains Dr Martinache, "The first can be corrupted by optical problems, and we discard this. Kernel phase interferometry can then focus exclusively on information in the image which is essentially immune to the noise. It is like a noise-cancelling headset on an aeroplane: you flick off the noise and you can suddenly detect all these faint signals nobody else could find."

Pope's research unleashed this method in the hunt for companions to the intriguing objects known as brown dwarfs which occupy the no-man's-land in mass between gas giant planets like Jupiter, and the smallest, dimmest stars.

"Brown dwarfs are like a missing link between stars and planets, and by studying them we learn more about how the great diversity of star systems in the universe came to be formed," said Pope.

"Although they are incredibly faint, so we never see them except with large telescopes, they are actually very common. Most importantly, nobody is quite sure how they can be formed, and they present a tricky challenge to just about all theories for how matter collapses to form compact bodies like stars and planets … In particular, one of the key tests is to find how often brown dwarfs are found in pairs."

This pairing, or binary factor, is quite high for stars - the in-joke among astronomers is that three in every two stars is a binary.

"What my work here has shown is that it is in fact also higher than previously thought for brown dwarfs too," said Pope.

"You can't help but feel a little poignancy for brown dwarfs … out in the cold reaches of the galaxy, never to see a sunrise and doomed to slowly freeze as generations of stars around them are born and die," said Professor Peter Tuthill, Pope's research supervisor.

"I guess Ben's work gives the poets in us a little solace, in that more of them than we expected are in a stately orbital dance with a partner that will still be going when our own sun has lived its entire life and is but a memory."

Mr Pope's award marks a hat-trick for the University's Sydney Institute for Astronomy which has won this national prize three years in a row with past winners Alison Hammond (2012) and Barnaby Norris (2011).

Dancing in the Dark: New Brown Dwarf Binaries from Kernel Phase Interferometry, Pope, Martinache and Tuthill, is now published in the Astrophysics Journal.